[css-pseudo] typo, and make example look better

Author: tabatkins

css-pseudo/Overview.bs

@@ -737,7 +737,7 @@ Overlapping Pseudo-element Interactions</h2>
         the ''::first-letter'' boundaries are tightly wrapped around the first letter text,
         and ''::first-letter'' is constrained to exist solely on the first formatted line.
       <li>
-        the ''::first-line'' start is inserted inserted just inside the containing block's element boundary,
+        the ''::first-line'' start is inserted just inside the containing block's element boundary,
         and its end after the close of all content on the line
     </ul>
 
@@ -758,16 +758,17 @@ Overlapping Pseudo-element Interactions</h2>
 
     Assuming that a line break will occur before the word "ends",
     the <a>fictional tag sequence</a> for this fragment might be:
-    <pre>
-      &lt;P&gt;
-      &lt;P::first-line&gt;
-      &lt;P::first-letter&gt;
-      S
-      &lt;/P::first-letter&gt;ome text that
-      &lt;/P::first-line&gt;
-      ends up on two lines
-      &lt;/P&gt;
-    </pre>
+    <xmp>
+      <p>
+        <p::first-line>
+          <p::first-letter>
+            S
+          </p::first-letter>
+          ome text that
+        </p::first-line>
+        ends up on two lines
+      </p>
+    </xmp>
   </div>
 
 <h2 id="cssom">